Antiinflammatory imidazothiazoles

ABSTRACT

Certain imidazothiazoles and thiazolopyrimidines have been found to prevent and inhibit the formation of granuloma tissue in animals. This result is accomplished by administering to the animal subject a therapeutically effective amount of a compound having the formula: ##STR1## wherein R is hydrogen or methyl, R&#39; is hydrogen, lower alkyl or thioalkyl, carboxy methyl, or phenyl; R&#34; is lower alkyl, 2-benzofuranyl, naphthyl, phenyl, or mono- or disubstituted phenyl. The hydrated precursors of certain of these compounds as well as the acid addition and quaternary salts of both the compounds and their hydrated precursors may be employed.

BACKGROUND OF THE INVENTION

Many compounds are known which exhibit some degree of antiinflammatoryactivity.

For example, British Pat. No. 1,099,389 discloses certain2,4-disubstituted thiazoles which are known to be antiinflammatory.However, these compounds suffer from certain inherent deficiencies whichlimit their utility as antiinflammatory drugs. Also, in U.S. Pat. No.3,796,800 is disclosed another group of thiazoles which exhibitantiinflammatory properties. These compounds are generally identified bythe formula: ##STR2## wherein R is lower alkyl (e.g., --CH₃), orN-aminocarbamoyl; R" and R'" are independently selected from the groupconsisting of hydrogen, lower alkyl (e.g., --C₂ H₅) and lower acyl(e.g., --COCH₃); and R' is hydrogen, CONHR₁ or CONR₂ R₃, wherein R₁ isphenyl, mono-, di- or tri-(lower) alkylphenyl, cyclohexyl, or amino; R₂is lower alkyl (C₁ -C₃); R₃ is lower alkyl (C₂ -C₃) or phenyl; or R₂ andR₃ together with the nitrogen atom form a morpholino ring, andpharmaceutically acceptable acid addition salts thereof, such as thehydrochloride.

While the above compounds evidence antiinflammatory properties, theyalso exhibit certain other properties which limit their utility as suchdrugs.

From the Canadian Journal of Chemistry (Vol. 42, pg, 2847, 1969) certain[2,1-b] thiazoles and thiazolo [3,2-a] pyrimidines are known asanthelmintics. 3-(Hydroxy- or methoxy)-phenyl-5,6-dihydroimidazo-[2,1-b]thiazoles are known from U.S. Pat. No. 2,969,369 to have a variety ofpharmaceutical activities, including an antiinflammatory effect.Further, U.S. Pat. No. 3,860,718 describes the use of quaternary7-substituted imidazo [2,1-b] thiazolium compounds as hypoglycemicagents (blood-sugar lowering agents), but no disclosure can be foundtherein which would indicate that such compounds have antiinflammatoryproperties.

STATEMENT OF THE INVENTION

Therefore, it is an object of the present invention to provide effectiveantiinflammatory compositions containing as the active ingredientsthereof certain imidazothiazoles and thiazolopyrimidines.

It is a further object of the present invention to provide a method forpreventing and inhibiting the formation of granuloma tissue in animalsemploying certain imidazothiazoles and thiazolopyrimidines.

It is a still further object of the present invention to provide animidazothiazole and certain hydrated precursors of imidazothiazoles andthiazolopyrimidines which have pharmaceutical activity.

These and further objects of the present invention will become apparentto those skilled in the art from the specification and claims whichfollow.

There has now been found a pharmaceutical preparation in dosage unitform, the active ingredient of which consists of a nontoxicantiinflammatory amount of at least one compound of the formula:##STR3## wherein n is 2 or 3; R is hydrogen or methyl; R' is hydrogen,C₁ -C₃ alkyl or thioalkyl, phenyl, or carboxy methyl; and R" is C₁ -C₄alkyl, 2-benzofuranyl, naphthyl, phenyl, or mono- or di-substitutedphenyl, and acid addition and quaternary salts thereof.

A method of preventing and inhibiting the formation of granuloma tissuein an animal subject has further been found, which method comprisesadministering to said animal a nontoxic antiinflammatory amount of atleast one such compound.

There have further been found3-(2-benzofuranyl)-5,6-dihydro-4H-imidazo-[2,1-b] thiazole and certainhydrated precursors of imidazothiazoles and thiazolopyrimidines havingthe formula: ##STR4## wherein n is 2 or 3; R is H or CH₃ ; and Y isphenyl or p-chloro- or p-methoxyphenyl. These compounds also haveantiinflammatory effect and may be employed in the acid addition orquaternary salt form.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Compounds which are the active ingredients of the present invention fitthe general formula: ##STR5## In this formula, when n is 2, thecompounds are designated generally as substituted5,6-dihydro-4-H-imidazo-[2,1-b] thiazoles. When n is 3, the compoundsare designated as substituted tetrahydrothiazole-[3,2-a] pyrimidines.The substituent R, of which 1 may be present on each methylene group,represents either hydrogen or methyl. The groups represented by R'include hydrogen, C₁ -C₃ alkyl (especially methyl and ethyl) andthioalkyl (especially thiomethyl), carboxy methyl; and phenyl. Themembers fitting the definition for R" include C₁ -C₄ alkyl (especiallymethyl and tertiarybutyl), 2-benzofuranyl, naphthyl, phenyl, and mono-or disubstituted phenyl (especially wherein the substituents areelectronegative and in the "para" position, such as Cl, Br, NO₂, OCH₃,and 3,4-dichloro- or dimethyl). A preferred and novel compound at thistime is 3-(2-benzofuranyl)-5,6-dihydro-4H-imidazo [2,1-b] thiazole(including salts thereof). Preferred and novel hydrated precursors ofthe above formula are those corresponding to the formula: ##STR6##wherein n is 2 or 3; R is H or methyl; and Y is phenyl or p-chloro- orp-methoxyphenyl.

While the compounds themselves exhibit excellent antiinflammatoryactivity, they may be and often are employed in the form ofpharmacologically acceptable acid addition or quaternary salts thereof.For example, one may employ acid halides, such as HBr or HCl, ortartaric acid, to form the addition salts or alkyl halides and the like,such as propargyl bromide, for quaternization. The criteria for choosingand methods for preparing salts suitable for administration are wellknown to those skilled in the art.

In preparing the pharmaceutical compositions of the present invention inunit dosage form, a nontoxic, antiinflammatory amount of one or more ofthe compounds of the present invention is incorporated with theappropriate carriers and/or diluents. Generally, the amount foradministration will be from about 10 to 500 milligrams/kilogram/day ofbody weight, preferably from about 50 to 300 mg/kg/day.

For example, in the case of a tablet, the composition will comprise, inaddition to the active ingredient, fillers, binders, and diluents suchas lactose, methylcellulose, talc, gum tragacanth, gum acacia, agar,polyvinylpyrrolidone, stearic acid, and/or corn starch, etc. In the caseof a liquid suspension for oral administration, the composition willcomprise, in addition to the active ingredients, a filler such as sodiumcarboxymethylcellulose and/or syrup, e.g., a glycerine based syrup. Inthe case of a parenteral solution or suspension, the composition willcomprise, in addition to the active ingredient, a suitable solvent orother liquid such as a saline solution. In the case of a topicalointment, a vehicle such as petroleum jelly or hydrophillic petroleum issuitable.

The compounds employed in the instant invention may be prepared by thecondensation of an α-haloketone with (1) 2-mercaptoimidazoline or asubstituted derivative to yield the desired (substituted)5,6-dihydro-4H-imidazo-[2,1-b] thiazole or (2) with1,2,3,4-tetrahydro-2-pyrimidinethiol or a substituted derivative toyield the desired (substituted) tetrahydrothiazolo-[3,2-a] pyrimidine.Reference to such standard preparations is set forth in the CanadianJournal of Chemistry, Vol. 47 (1969) at page 2843. Examples of thepreparation of certain compounds of the instant invention follow.

EXAMPLE 1

To a refluxing solution of 3-benzoyl propionic acid (18 gm) in CHCl₃(100 ml) was added bromine (16.2 gm) in CHCl₃ (100 ml). After 10 minutesof refluxing, the reaction mixture was cooled and the CHCl₃ removed invacuo. 2-Imidazolidine (10.2 gm) in absolute ethanol was added and thereaction mixture heated to reflux for 1 hour. The reaction mixture wascooled and the precipitate separated by filtration. The product wasrecrystallized from 95% ethanol. The isolated product (5.5 gm) has amelting point of 258°-263° C. and was found to be3-phenyl-5,6-dihydro-4H-imidazo[2,1-b] thiazo-2-yl acetic acidhydrobromide.

EXAMPLE 2

Similarly, for the preparation of2-methylthio-3-t-butyl-5,6-dihydro-4H-imidazo-[2,1-b] thiazolehydrobromide, the procedure of Example 1 was followed except1-methylthiopinacolone (10.7 gm) was brominated (11.4 gm) for thedesired intermediate. ##STR7##

EXAMPLE 3

A solution of 7.41 g (0.05 mole) of N-butyrophenone and a trace of AlCl₃in 15 ml anhydrous ethyl ether was brominated using 8.0 g (2.65 ml; 0.05mole) of bromine. The ether and the bromine were removed by in vacuo.The resulting oil was diluted to 100 ml with absolute ethanol and mixedwith 5.809 g (0.05 mole) of 3,4,5,6-tetrahydro-2-pyrimidine thiol. Thismaterial was refluxed for 18 hours. The crude product which was obtainedon cooling the reaction mixture was recrystallized from 95% ethanol.Recovery was 8.09 g (49.74%) of a white solid which was analyzed andfound to be 2-ethyl-3-phenyl-4,5,6,7-tetrahydrothiazole[3,2-a]pyrimidine hydrobromide.

It should be noted that the intermediates, e.g., hydrated compounds, maybe produced by well known variations of the foregoing generaltechniques. For example, they can be obtained by not refluxing butsimply heating to a temperature of about 25° C.

EXAMPLE 4

The compounds of the present invention have pharmaceutical activity asantiinflammatory agents, effective in the prevention and inhibition ofgranuloma tissue formation. The activity is demonstrated by a test whichinvolves the diminution of experimental edema induced in the hind paw ofa rat by the injection of carrageenin.

The procedure used for measuring the inhibition of carrageenin-inducededema is a slight modification of the method of Winter et al., Proc.Soc. Explt. Biol. Med. 111:544 (1962). The device used for measurementof the paw volume is an adaptation of the water displacement proceduredescribed by Adamkiewicz et al., Can. J. Biochem. Physiol. 33:332(1955). The above compounds were studied for their effectiveness inpreventing the edema caused by the intraplantar injection of 0.05 ml ofa sterile 1.0% solution of carrageenin. Compounds were administeredorally, except when indicated as intraperitoneally (i.p.), one hourprior to the injection of the carrageenin into the left hind paw ofrats. At peak swelling time (3 hours) the volume of edema was calculatedby differential paw volumes.

Table I (in which Ph = phenyl) sets forth results obtained at theindicated dosages with compounds (or their salts) of the formula:##STR8##

                                      TABLE I                                     __________________________________________________________________________    Com-                             Dose Reduction                               pound                                                                              n= R=   R'=   R"=     Salt  (mg/kg)                                                                            %                                       __________________________________________________________________________     1   2  H,H  H     Ph      HBr   50   47                                       2   "  "    H     3,4-diCH.sub.3 Ph                                                                     "     "    27                                       3   "  "    SCH.sub.3                                                                           C(CH.sub.3).sub.3                                                                     "     "    26                                       4   "  "    C.sub.2 H.sub.5                                                                     Ph      "     25   41                                       5   "  "    C.sub.2 H.sub.5                                                                     p-ClPh  "     "    33                                       6   "  "    CH.sub.3                                                                            "       "     "    45                                       7   "  "    H     p-BrPh  "     50   70                                       8   "  "    H     C(CH.sub.3).sub.3                                                                     H tartrate                                                                          "    56                                       9   "  "    H     CH.sub.3                                                                              HCl   "    46                                      10   "  "    H     α-naphthyl                                                                      HI    "    58                                      11   "  "    H     C(CH.sub.3).sub.3                                                                     none  "    48                                      12   "  CH.sub.3,H                                                                         H     C(CH.sub.3).sub.3                                                                     HBR   "    54                                      13   "  CH.sub.3,H                                                                         H     CH.sub.3                                                                              HCl   "    24                                      14   "  H,H  CH.sub.3                                                                            Ph      HBr   "    49                                      15   "  H,H  Ph    CH.sub.3                                                                              HBr   "    53                                      16   "  CH.sub.3,H                                                                         H     p-ClPh  HBr   "    58                                      17   "  CH.sub.3,H                                                                         H     p-NO.sub.2 Ph                                                                         HBr   "    48                                      18   "  CH.sub.3,H                                                                         H     3,4-diClPh                                                                            HBr   "    42                                      19   "  H,H  CH.sub.2 COOH                                                                       Ph      HBr   100ip                                                                              24                                      20   "  "    H     Ph      3,4-diCl-                                                                           20   36                                                                 benzyl Cl                                          21   "  "    H     p-BrPh  none  40   49                                      22   "  "    H     "       propargyl Br                                                                        100  36                                      23   "  "    H     "       α-methyl                                                                      40   27                                                                 propargyl                                                                     Cl                                                 24   "  "    H     "       4-chloro-2-                                                                         60   20                                                                 buteneyl Cl                                        25   "  "    H     CH.sub.3                                                                              none  150  44                                      26   "  "    H     CH.sub.3                                                                              propargyl                                                                           40   31                                                                 Br                                                 27   "  "    H     2-benzo-                                                                              HBr   40   40                                                         furanyl                                                    28   3  3H   H     p-ClPh  "     25   29                                      29   "  "    C.sub.2 H.sub.5                                                                     Ph      "     50   76                                      30   "  "    H     Ph      "     40   25                                      31   "  "    CH.sub.3                                                                            Ph      "     40   48                                      32   "  "    H     p-NO.sub.2 Ph                                                                         "     25   20                                      33   "  "    CH.sub.3                                                                            p-ClPh  "     10   22                                      __________________________________________________________________________

All compounds show a positive effect, which may be increased by the useof larger dosages.

EXAMPLE 5

Following the procedure set forth in Example 4, hydrated compoundsaccording to the following formula were evaluated for antiinflammatoryeffect with the results shown in Table II: ##STR9##

                  TABLE II                                                        ______________________________________                                        Com-                              Dose   Reduction                            pound n=     Y=        R=   Salt  (mg/kg)                                                                              (%)                                  ______________________________________                                        34    2      Ph        H    HBr   100    70                                   35    2      Ph        CH.sub.3                                                                           "     150    68                                   36    2      p-ClPh    H    "     25     57                                   37    3      Ph        H    "     50     52                                   38    3      p-ClPh    H    "     100    76                                   39    3      p-CH.sub.3 OPh                                                                          H    "     40     27                                   ______________________________________                                    

EXAMPLE 6

Certain of the compounds of the invention were further tested todetermine their ED₅₀ values. The ED₅₀ value is defined as that dosewhich reduced edema formation by about 25% or more compared with themean control response (parallel run) in 50% of the animals. Typicalresults of these tests appear in Table III.

                  TABLE III                                                       ______________________________________                                        ED.sub.50 vs. CARRAGEENIN ASSAY                                                        Dose           ED.sub.50 Confidence                                  Compound (mg/kg)        (mg/kg)   Limits                                      ______________________________________                                        1        25, 75, 100, 150                                                                             25        18-32                                       9        25, 50, 75, 100                                                                              20        16-24                                       ______________________________________                                    

EXAMPLE 7

Next, certain of the compounds were subjected to a secondary screendesignated the adrenalectomized assay. In this series of tests, themethod used was identical to that described above, except that theanimals used were adrenalectomized several days prior to assay. Sincethe results in the nonadrenalectomized animals were similar to thoseobtained in the adrenalectomized animals, it can be inferred that theantiinflammatory activity of the test compounds was not caused by therelease of endogeneous adrenocortical steriods.

The results of this test are given in Table IV.

                  TABLE IV                                                        ______________________________________                                        Adrenalectomized Sprague Dawley Male Rats                                     (Charles River)                                                               Compound    % Reduction   Dose at mg/kg                                       ______________________________________                                         1          32            50                                                   4          31            25                                                   5          15            25                                                   6          19            25                                                   8          23            25                                                   9          46            25                                                  10          18            50                                                  16          16            50                                                  17          60            50                                                  29          18            25                                                  ______________________________________                                    

EXAMPLE 8

Selected compounds were further subjected to advanced evaluations.Specifically, in view of the interesting activity of compounds 1 and 9,those compounds were further subjected to the adjuvant-induced arthritistest. This test requires one month (from day 0 to day 31). In the first17 days (0-17), the disease is in a developing stage, while for theremainder of the month (18-31) the disease is fully developed. Theresults of this test, given in terms of percent reduction of swelling inthe hind paw of the rat are shown in Table V.

The method is essentially that of Newbould, Brit. J. Pharmacol. 21: 127,1963. The test compounds were studied in the developing arthritis stateand in the established arthritic state. Separate groups of 12 rats wereadministered the compounds orally using methylcellulose as the vehicle.In the study on the developing disease, administration of the testcompounds begins on day 1 and on day 2 each animal is injected with .05ml/kg of a 0.5% suspension of heat-killed Mycobacterium tuberculosisinto the planter surface of the left hind paw. Foot volumes weremeasured by a water displacement device on the day of administration ofthe Mycobacterium and again on days 3, 10 and 17. The test compoundswere administered once daily. Body weights were recorded daily and theanimals were examined for the spread of the inflammation and the degreeof secondary lesions. For study in the established disease, anothergroup of rats are injected with the Mycobacterium and foot volumes aremeasured. After 20 days volumes are again measured and administration ofthe test compounds begins and continues for 11 days. Foot volumemeasurements are repeated on day 27 and day 31. The extent of the spreadof the inflammation and the degree of lesions are recorded daily as arethe body weights. The effect of the test compounds is measured by thepercentage reduction in left hind paw volumes as compared to the hindpaw volumes of the control groups.

                  TABLE V                                                         ______________________________________                                        ADJUVANT ARTHRITIS TEST IN RATS                                               % EDUCTION IN SWELLING-HIND PAWS                                                         Days                                                                             Developing   Developed                                          Dose          (propylactic)                                                                              (therapeutic)                                      Compound                                                                              (mg/kg)  3       10   17   20   27   31                               ______________________________________                                        1       20       18      13   18   5     0   0                                        40       10      21   43   4    14   8                                9       24       21      23   15   5     0   0                                        50       18      17    6   3     3   7                                ______________________________________                                    

In addition to the reduction in inflammation indicated in Table V, alessening in the degree of secondary lesions was observed.

We claim:
 1. A pharmaceutical antiinflammatory preparation in dosageunit form comprised of a pharmaceutical carrier and an activeingredient, the active ingredient of which consists of a nontoxicantiinflammatory amount of a compound of the formula: ##STR10## whereinn is 2; R is hydrogen or methyl; R' is hydrogen, C₁ -C₃ alkyl orthioalkyl, phenyl, or carboxy methyl; and R" is C₁ -C₄ alkyl,2-benzofuranyl, naphthyl, phenyl, or mono- or disubstituted phenyl, oran acid addition or quaternary salt thereof.
 2. A preparation as inclaim 1 wherein the antiinflammatory amount is within the range of 10 to500 mg/kg/day.
 3. A preparation as in claim 1 wherein the compound ispresent as the HBr salt thereof.
 4. A pharmaceutical antiinflammatorypreparation in dosage unit form comprised of a pharmaceutical carrierand an active ingredient, the active ingredient of which consists of anontoxic antiinflammatory amount of a compound of the formula: ##STR11##wherein n is 2; R is hydrogen or methyl; and Y is phenyl or p-chloro- orp-methoxyphenyl, or an acid addition or quaternary salt thereof.
 5. Apreparation as in claim 4 wherein the amount of compound is within therange of 10 to 500 mg/kg/day.
 6. A preparation as in claim 1 wherein thecompound is 3-(2-benzofuranyl)-5,6-dihydro-4H-imidazo-[2,1-b] thiazole.7. A method of preventing and inhibiting the formation of granulomatissue in an animal subject, which method comprises administering tosaid animal a nontoxic antiinflammatory amount of a compound of theformula: ##STR12## wherein n is 2; R is hydrogen or methyl; R' ishydrogen, C₁ -C₃ alkyl or thioalkyl, phenyl, or carboxy methyl; and R"is C₁ -C₄ alkyl, 2-benzofuranyl, naphthyl, phenyl, or mono- ordisubstituted phenyl, or an acid addition or quaternary salt thereof. 8.A method as in claim 7 wherein the amount administered is within therange of 10 to 500 mg/kg/day.
 9. A method of preventing and inhibitingthe formation of granuloma tissue in an animal subject, which methodcomprises administering to said animal a nontoxic antiinflammatoryamount of a compound of the formula: ##STR13## wherein n is 2; R ishydrogen or methyl; and Y is phenyl or p-chloro- or p-methoxyphenyl, oran acid addition or quaternary salt thereof.